linux-kernel - Re: PCI PM: Restore standard config registers of all devices early

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Date:	Tue, 3 Feb 2009 00:00:17 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jesse.barnes@...el.com>,
	Andreas Schwab <schwab@...e.de>, Len Brown <lenb@...nel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: PCI PM: Restore standard config registers of all devices early

On Monday 02 February 2009, Benjamin Herrenschmidt wrote:
> On Mon, 2009-02-02 at 14:05 -0800, Linus Torvalds wrote:
> > Well, I don't think anybody wants to (or necessarily has the ability) 
> > touch ACPI internals.
> > 
> Somebody has a rough idea of what underlying kernel support ACPI uses ?
> I know from discussions with Len that it's mostly mutexes... timers
> too ?

Please see my last message in this thread (just sent).

> It might end up being trivial to make it safe to call early with
> interrupts off with the trick you mentioned, since it's really just the
> same as boot as you mentioned.. ie, it's actually safe to take mutexes
> etc... since we -know- no other CPU is running and we aren't scheduling
> etc...

But we can't tell no one is holding the mutex in question, AFAICS.

I'm afraid we'd really need a special "no mutexes, no GFP_KERNEL allocations"
code path for that.

Thanks,
Rafael
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